1. Field of the Invention
The present invention relates to x-ray diagnostic systems including an image intensifier chain, and in particular to such a system with a means for automatically disconnecting the x-ray tube from the high voltage generator if the absence of selected signals is detected.
2. Description of the Prior Art
An x-ray diagnostic system having an x-ray tube connected to a high voltage generator and having an image intensifier television chain is described in German OS No. 2 803913, corresponding to U.S. Pat. 4,335,311. This system includes a control loop for monitoring the x-ray dose rate and maintaining the dose rate at a constant level on the basis of an adjusted nominal value. The actual value of the dose rate is formed by a sensor disposed in the light path between the output of the x-ray image intensifier and the television camera.
In any x-ray diagnostic system, it is possible that inspite of the presence of x-radiation, no image appears at the output of the x-ray image intensifier. It is also possible that even if a signal appears at the output of the x-ray image intensifier, a video or television signal may still be lacking. The absence of such signals may be caused by any number of disturbances or malfunctions. In conventional x-ray diagnostic systems of the type identified above, the patient and the technician or physician are unnecessarily exposed to radiation because the x-ray source continues to emit x-rays, even though no usable signal is present. In addition, unnecessary loading of the high voltage generator and the x-ray tube occurs as a result of the dose rate being automatically raised to a higher level by the dose rate control loop.